Jumping lunges are one of my favorite body weight exercises, you can pretty much do them anywhere. I am prone to randomly busting them out in my house. They are definitely difficult, in just 30-45 secs you are exhausted, but they work! In this video I keep my hands above my head but they are easier if you keep them on your hips or move them for momentum.
20 Jumping Lunges (w/ In for the Kill [skream remix] by La Roux~the last min. of the song):